Cold working of metal into a predetermined shape is commonly undertaken in extrusion and coining operations. Extrusion techniques are usually multi-stage with the solid metal blank being successively exposed to various punch and die operations until the desired end product is achieved. The punch compress the metal to exceed the compressive yield strength thereof, such that the metal will flow and assume the shape defined by the die and punch. Because the process is multi-staged, the extent of deformation in any one stage is small and controllable such that the precision of the final product is a direct result of the multi-stage operation. Obviously multi-stage operations are more expensive to operate than single-stage operations; however, the accuracy required dictates the use of multi-stage processes.
Cold working a metal by coining is commonly used; however, this operation normally requires the entire blank to be worked. The resulting product has good definition and tolerances can be controlled. However, in some circumstances it is not desirable to have the entire blank undergo the coining operation. In yet a further cold working metal process, the end of a blank is loaded compressively with a portion of the blank sidewall at one end left unsupported. With sufficient load, the compressive yield strength of the material is reached causing the metal to be upset and flow into the unsupported area. This type of process may be used in forming the head on a valve stem, the head on a nail, etc.
Mechanical pipe unions and pipe fittings for equipment are presently made by a casting operation or a welding operation. For example, a meter swivel used in the gas industry, which is essentially a small length of pipe with a flange and a spigot at one end, is produced by either casting the entire unit or by welding a flange to the body of the swivel. Swivels produced by either of these methods are somewhat prone to leaks caused by porosity in the cast swivels and cracks or flaws in the units that have welded flanges. Obviously, these units could be produced by a series of machining operations overcoming the quality control problem; however, the production costs could not be justified.
The present invention seeks to mitigate the problems experienced by the prior art structures by providing a simple production process which allows the manufacture of a number of mechanical piping connectors at reduced costs and improved quality.